.Ddesign {
    width: 100%;
    height: 100%;
    display: flex;
}

.app-left {
    width: 300px;
    padding: 20px;
    border-right: 1px solid #ccc;
}

.left-item {
    margin: 10px 0;
}

.app-right {
    flex: 1;
    padding: 20px;
}